#include<bits/stdc++.h>
using namespace std;

using i64 = long long;

i64 n, m, k;
bool flag;

int main()
{
    while (cin >> n >> k) {
        __int128 q = 1;
        k = min(k, n - k);
        flag = 0;
        for (int i = 1;i <= k;i++) {
            q *= (n - i + 1);
            q /= i;
            if (q > 1e18) {
                cout << 1000000000000000000 << endl;
                flag = 1;
                break;
            }
        }
        if(!flag)
        cout << (i64)q << endl;

    }
}